For all the advantages of the sidestick, the 'outdated' traditional yoke, retained by Boeing, (much to the disdain of many Airbus fans here), allows the other pilot(s) in the cockpit to be easily and clearly aware of the inputs, whether appropriate or inappropriate, being made by the other pilot, where the sidestick does not. In a really critical and highly unusual situation like the AF447 crew found themselves in, this is no small matter.
Even if linked sidesticks or yokes had been installed, would it have been noticed by the dummy in the left seat of AF447? As I recall, there actually was discussion about the fact that the the other dummy in the right seat had been pulling up ever since the autopilot disengaged. Clearly, they thought they were playing a video game, instead of flying an airplane. When flying an airplane with the automatics, there still are real-world consequences.
Aviate, Navigate, Communicate. Apparently no one does the first one anymore.